The present invention relates to a method of repairing open defects in thin film conductor lines on a substrate, such as a printed circuit board or a multi-layered ceramic substrate, by diffusion bonding a conductive metal line from a support sheet to the open defect region of the conductor. Specifically, a pattern of conductive lines is formed onto a support sheet from which one line is selectively bonded in position to repair an open defect in a conductor line by the use of a combination of laser energy and ultrasonic energy.
The manufacturing of very fine circuit conductors in a substrate such as a high density printed circuit board or a multi-layer ceramic substrate is characterized by defects which are inevitably produced. One prior method of repairing opens in conductors relies upon filling the gap with copper deposited by decomposition of an organo-metallic gas induced by laser chemical vapor deposition. The method has serious deficiencies resulting from the use of cold metal deposition which inhibits the formation of a sound metallurgical bond. Another problem encountered with the prior method is the poor mechanical reliability of the repair segment which is manifest by delamination during spin cleaning or thermal cycling of the substrate. The prior method also requires an additional processing step in order to remove any thin contamination or metallic film such as a chromium layer often found on the surface of circuit lines, thereby extending the time required to effect the repair.
U.S. Pat. No. 4,704,304 describes a repair method in which an unpatterned repair metal film is placed over a general area of an open defect in a conductive line on a substrate. The resultant assembly is heated to cause diffusion bonding between the repair metal and conductive lines. The repair area is then subjected to ultrasonic energy while being disposed in a liquid in order to remove metal bridges between conductors without removing repair metal bridges over opens in the conductive lines.
U.S. Pat. No. 4,636,403 describes a photomask repair method in which a surface is coated with a layer of metal-organic compound which is exposed to a laser beam in the region of a defect until a patch is formed. After the patch is formed excess unexposed compound remaining on the substrate surface is removed with an appropriate solvent.